5.6- Fires in nature Flashcards
what is a wildfire?
- uncontrolled rural fire- they destroy forests, grasslands and other areas of vegetation
wildfires are known as what in Australia and North America?
bushfires
there are 3 main types of wildfire and all 3 can be present at the same time:
- ground fire: slow smouldering ground base fire e.g. dry organic peat. No flames.
- surface fire: the burning of leaf litter and low-lying vegetation. Can be high or low intensity.
- crown fire: fire moves rapidly through the canopy. This fire has a dramatic effect on forested areas
what are the conditions that encourage wildfires?
- vegetation type/fuel characteristics
- climate and recent weather conditions
explain how vegetation type/fuel characteristics encourages wildfires
- influences the intensity (heat output) and rate of speed (degree of threat)
- grassland= low heat output whereas forested areas= high heat output
- eucalyptus and pine contain a lot of oil= burn easily
- eucalyptus shed long strips of bark during a fire (firebrands) which can encourage the spread
- in general, fine, dry material catches fire easily e.g. long grasses/twigs
explain how climate/ recent weather conditions encourage wildfires
- rainfall sufficient for vegetation to grow (fuel)
- a distinct dry season- causes vegetation to dry up and become more flammable= why low risk of wildfires in UK
- strong winds provide oxygen and help the fire spread and can in some circumstances, trigger lightening storms which are a natural trigger of wildfires
- cyclical climate events like El Niño can cause favourable conditions
what is El Niño?
occurs every 6-8 years and involves the warming of the Pacific Ocean off the West Coast of South America. It affects global patterns of temperature and rainfall
what are the main natural causes of wildfires?
- lightning
- volcanic eruptions
- heat transfer heats vegetation ahead of the flames causing the fire to spread more rapidly- hot air rises (heat transfers vertically) which is why fires are so good at climbing. Experiments in Australia found that fires in a 20 degree slope advance 4 times the rate as fires on ground level
- firebrands can be blown ahead of the flames and ignite new areas of forest- spot fires. Firebrands can also roll down hills and create spot fires
do natural or human causes, cause the majority of wildfires?
human causes
what are the main human causes of wildfires?
- discarded cigarettes
- poorly controlled campfires
- arson
woodland that is particularly close to urban areas is most vulnerable of this sort of activity and known as ‘wildland-urban interfaces’
where are good examples of ‘wildland-urban interfaces’?
Los Angeles and Sydney
what are a few primary social impacts?
- loss of life
- displacement (people forced to temporarily move elsewhere)
- disruption to power supplies if power lines damaged by strong winds
what are a couple secondary social impacts?
- possible need for new employment and income stream
- behavioural adaptions based on wildife experience e.g. people may have to abide by new rules and regulations
what are a couple primary economic effects?
- destruction of businesses
- loss of livestock and crops
what are a few secondary economic effects?
- cost of building or potential relocation
- replacement of farm infrastructure,crops, livestocks etc
- costs of future preparedness and mitigation strategies
what are a few primary environmental impacts?
- destruction of habitats and ecosystems- death of organisms impacts food chains and webs
- short- term surge of carbon dioxide due to burning of trees (sinks)!!
- atmospheric pollution resulting from smoke and water pollution as toxic ash gets washed into water courses
what are a couple secondary environmental impacts?
- increased carbon emissions impact on the (enhanced) greenhouse effect and climate change- depending n scale
- lack of trees and vegetation causes depletion of nutrient stores, increased leaching and increased risk of flooding (reduced interception)
what are a couple of primary political effects?
- actions of emergency services
- pressure on local authorities and emergency services to coordinate and prioritise responses in the immediate aftermath
what are a couple of secondary political effects?
- develop strategies for preparedness and mitigation
- decisions regarding replanting forests, compensation, future regulations etc
what are some short-term responses to wildfires?
- emergency response teams attempting to put fire out
- warning shared via social media platforms, TV and radio
- evacuation
- spraying water onto roofs of houses to prevent fire igniting them
what is involved in long-term responses?
- preparedness
- mitigation
- adaption
- prevention
what is involved in preparedness?
- households write an emergency plan and buy in emergency supplies of food, water and medicine
- authorities make emergency shelters
- warnings are released using social media, TV and radio
- red flag warning used in USA when weather conditions are perfect for serious fires (low humidity, strong winds and dry fuels)- residents in vulnerable areas are to be alert
what is involved in mitigation?
- satellites with infrared can detetc thermal variation
- NASA developing drone tech to survey large areas
- disaster aid and insurance can mitigate the effects of wildfires (to people and property in particular)
what is involved in prevention?
- public education to highlight the risks of campfires and BBQs in vulnerable areas
- fire beaters available near recreational spaces so the public can put out small fires before they spread
HOWEVER natural e.g. lightning is much more difficult
what is involved in adaption?
- planning regulations to enforce use of non-flammable building materials used in vulnerable areas
- fire breaks created in forests to halt fire from spreading. However, fires in strong winds can ‘jump’ fire breaks. In the 2016 Alberta fire the wildfire jumped a 1km wide river
- there is a school of thought that fires are a natural regenerative process within a forest ecosystem and they should be allowed to run their course
